An acoustic transducer includes a passive diaphragm and an active diaphragm. The active diaphragm electromechanically couples to an electric drive element and the passive diaphragm is configured to acoustically couple with pressure changes induced by excursions of the active diaphragm. The active diaphragm has an outer perimeter and an inner perimeter, with the X-Y (horizontal) points on the outer perimeter of the passive diaphragm coinciding on or within X-Y points on at least the outer perimeter of the active diaphragm over a common, orthogonal Z coordinate so that the passive diaphragm projects a shape that falls on or within an area of the active diaphragm. In some cases, the inner perimeter of the active diaphragm may define a bounded area for the active diaphragm, the passive diaphragm having an outer perimeter that axially, superimpositionally coincides on or within the inner perimeter of the bounded area.